The Anaconda repo states that:
Public mirrors of this are not allowed without express permission from Anaconda, Inc.
If someone builds a public reverse proxy to https://repo.continuum.io/pkgs/ , is it considered as a violation of terms above?
A reverse proxy is a service that does not store upstream packages on a local disk like a mirror server, instead, every time a user requests a package from reverse proxy, the proxy server fetches it just in time from upstream and send it back to the user. From the users perspective, it behaves just like a mirror with more delays. However, reverse proxy is also broadly used in public networks.
For more details, https://opensource.stackexchange.com/questions/4471/agpl-violation-using-reverse-proxy is probably a good explanation.